1. Field of the Invention
This invention relates generally to electric cars, and more particularly to a drive system for an electric car which includes a DC drive motor, an AC drive motor, and an auxiliary engine which powers the AC drive motor through an alternator.
2. Description of the Prior Art
The conventional electric car includes a DC motor energized through a power controller by a bank of direct current storage batteries and a transmission for propelling traction wheels which is driven by the DC motor. The range of the conventional electric car is limited by factors such as the weight of the vehicle, aerodynamic drag, the energy storage capability of its batteries, and the efficiency of the drive motor and other equipment powered by its batteries.
One approach to extending the effective travel range is to provide an auxiliary internal combustion engine, a battery charging system and two banks of series-connected batteries which are periodically switched between operating and charging service as disclosed in U.S. Pat. No. 3,874,472. In that arrangement, one bank of batteries is charged by the auxiliary internal combustion engine as the other bank of batteries energizes a direct current drive motor. By switching the two groups of batteries between operating and charging service at regular intervals, the effective range of continuous travel is substantially increased.
U.S. Pat. No. 3,650,345 discloses an arrangement including an internal combustion engine which extends the effective travel range of an electric car wherein the traction wheels are driven at low speeds by electric energy stored in a battery and at high speeds by the internal combustion engine which simultaneously recharges the battery.